SvMAGICAL_off(sv);
    SvREADONLY_off(sv);
    if (!(SvFLAGS(sv) & (SVf_IOK|SVf_NOK|SVf_POK))) {
        /* No public flags are set, so promote any private flags to public.  */
        SvFLAGS(sv) |= (SvFLAGS(sv) & (SVp_IOK|SVp_NOK|SVp_POK)) >> PRIVSHIFT;
    }